DESCRIPTION (Applicant's abstract verbatim): The goal of this project is to develop a miniature, catheter-based X-ray source for radiation therapy to prevent restenosis after percutaneous transluminal angioplasty. Restenosis affects 30 percent to 50 percent of angioplasty patients within six months of the procedure. Intravascular radiation therapy has been shown to be effective in preventing or significantly delaying restenosis in both coronary and peripheral vessels. Ongoing clinical trials of intravascular brachytherapy for restenosis use gamma or beta-emitting radioisotopes delivered to the angioplasty site via a guide catheter and withdrawn when sufficient dose has been delivered to the arterial segment. These radioactive devices have significant drawbacks, including limited dose rates and fixed dose-depth profiles, safety hazards to patient and medical personnel, and restrictions on transportation, storage and disposal. In Phase I, we evaluated the feasibility of developing a disposable, electrically-powered X-ray source small enough to reach the angioplasty site through a standard guide catheter. Advantages of the proposed source include on-off capability, high radiation dose rate, user-controlled dose-depth profile, and elimination of the regulatory and safety issues that accompany the use of radioactive materials. The Phase I results demonstrate the feasibility of constructing an ultra-miniature X-ray source with the required radiation dose rate and dose-depth characteristics. A fully operational X-ray source and delivery catheter will be developed in Phase II and tested in phantoms. PROPOSED COMMERCIAL APPLICATION: Approximately 1,000,000 coronary angioplasty procedures are performed worldwide each year. If radiation therapy for restenosis is proven effective in clinical trials, this represents a large market for catheter-based radiation devices. A flexible, catheter-based X-ray source also has many potential applications in radiation oncology.